Interpolating signal in high-speed telegraph circuits



Jan. 13, 1931. M. H. WOODWARD 1,788,477 INTERPVOLATING S'IGNAL IN HIGHSPEED TELEGRAPH CIRCUITS 3 Sheets-Sheet 1 Filed April 15, 1929 JETEETFTFTETWE v m mk MUTZUbmr o t n e D n 3 Jam 13, 1931. M. H. WOODWARD 1,

INTERPOLATING SIGNAL IN HIGH SPEED TELEGRAPH CIRCUITS Filed April 13,1929 3Sheets-Sheet 2 Jfwentor ,z'fjfmodwa/rd Jan. 13, 1931. .M. H.WOODWARD 1,788,477

INTERPOLATING SIGNAL IN HIGH SPEED TELEGRAPH CIRCUITS Filed April 15,1929 s Sheets-Sheet 3 3nventor M12. modward MUN (ltto'meg Patented Jan.13, 1931 UNITED STATES PATENT orr ca -MABION H. WOODWARD, F BROOKLYN,NEW YORK, ASSIGNOR TO THE WESTERN UNION TELEGRAPH COMPANY, OF NEW YORK,N. Y., A CORPORATION OF NEW YORK Application flied April 18,

My invention relates to telegraph systems and apparatus, and morearticularly, to systems in which the sigma s reaching the receiver areconsiderably attenuated. It is well known that in long telegraph systemsthe received signals are weakened and distorted to such an extent due toextraneous inductive effects and cable reactance that the receivingapparatus fails to respond thereto unless the signals are transmitted ata very low rate of speed. Inasmuch, however, as high speed signaling forthe cominercial operation eta cable is a necessity. receiving mechanismmust be provided which will respond to signals transmitted at acomparatively high signaling rate. One method for accomplishing thiswhich has met with great commercial success is to interpolate thetransmitted signals, i. e., to assume a normal transmission of periodicpositive and negative impulses, a receiver being'arranged to normallyvibrate its armature under local control as if in response to suchsignaling. During a signaling period comprising regular reversals ofpolarity, the weak received signals need not function as the receiveroperates as if in response to such signals.

A different condition exists, however, when a particular code includestwo successive s1g-. nals of the same character, but in such an v event,the rate of signaling has really decreased and by the time the second ofthese impulses is flowing the current in the receiver has reached anamplitude sufficient to become operative. Advantage is taken of this tocontrol the local relay operation, a magnetic force being createdopposing that of the local relay to prevent the armature from changingits position as if in response to two succeeding impulses of the samepolarity. It will beclear that the energy necessary to merely prevent anoperation of the armature is considerably less than is necessary toactually operate the armature. Hence both conditions comprised in codesignaling, i. e., periodic reversals of impulses and successive signalsof the same polarity, are properly interpolated. The receiver is thusoperated in accordance with high speed telegraph signals which areconsiderably attenuated. L

1929. Serial No. 354,907.

This method of signaling was first accomplished by'the Gulstad relay,comprising a local and a line winding. For interpolating the receivedsignals, the windings of the Gulstad relay are connected to impedancesthrough its armature in such a manner that alternate positive andnegative currents flow through the local winding when no current isreceived from the line. When the armature is in engagement with one ofits contacts, it

completes a circuit for its windin in such a direction that the armatureis t rown to its opposite contact, As this winding is thus energizedwith successive impulses of both polarities its armature is thrown toits two positions. in synchronism with. the rate at which the signalsare being transmitted.

Ifthe transmittedcode comprises alternate spacing and marking signalswhich, as explained above, are so attenuated that they do not affect thereceiving relay, the Gul'stad relay apparatus functions as described tosuccessively throw its armature to its alternate positions as if inresponse to the code signals. When on the other hand, a marking impulsefollows a marking impulse, the line current flowing in the line windinof the Gulstad relay isof sufiicient amplitude to -balance the effect ofthe current in the local winding tending to throw the armature to itsopposite position and hence the armature remains in p the same position.It willhe clear from the ;with. The Gulstad relay per se is not,however, provided with means for maintaining it in synchronous operationwith the signaling, dependence for thispurpose being placed on theconstants of the impedances employed in the circuits. Such reliance,however, for so important a phase of operation is unwar ranted andas isto he expected, from time ficulties experienced in maintaining theGulstad relay in synchronism. c,

Itwill be noted, however, that to ace our plish the desired results,Clokey resorts to elaborate, involved and complicated circuitarrangements and a large number of dis-- tributor sections, therebyrendering the sys tem inflexible and obviously undesirable.

As disclosed in the Clokey patent, the vibrating relay operates inresponse to local currents which flow continuously through its windingsand the received signals, in order to maintain the armature in itsoperated position in the event of a succession of two impulses of thesame polarity, must be of sufficient amplitude over this same period oftime to overcome the effects of the current in the local relay. Thereceived signals under consideration, are however, attenuated and hencemay not have the required continuous current amplitude. Clearly then, asystem such as proposed by Clokey, is marginal, for unless the receivedimpulse is continuously of sufiieient intensity, the local relaywinding, by reason of the continuous flow therethrough, will throw itsarmature to its alternate position in opposition to the current flowfrom the line relay.

Inasmuch as the Gulstad relay arrangement is employed tointerpolate veryweak and distorted received signals, it will. be clear that the localoperating circuits should be so adjusted with respect to line relayoperation that the attenuated signal can make its presence effective.Furthermore, in order to insure positive operations of the receiver, theinterpolation of the signals should take place a short interval inadvance of the receiver operation, in accordance. with the received codein order to prevent'chattering or a weakoperation of the receiver.

Accordingly, one object of my invention is to provide apparatus andcircuits at-the receiving station of a telegraph system forinterpolating signals with local currents of short duration and havingan amplitude sufficient to operate the armature but insufiicient tooperate the'armature in opposition to a received signal which may beconsiderably attenuated.

Another object of my invention is to 'pro- 2 vide means which are notmarginal for interpolating attenuated received signals.

A further object of my invention is to provide a simple arrangementrequiring a'minimum amount of apparatus for operating a relayarrangement of the Gulstad type in synchronism with signaling, impulses.

A; still further object of my'invention is to provide simple andreliablereceiving apparatus operating in response to attenuated and distortedsignals.

These and other objects will appear in the following detaileddescription in which refer-;

once is made to the accompanying drawings. Figure 1 is a diagram showingcurrent curves of code signals impressed on a signaling line at thetransmitting station.

Figure 2 illustrates the current curves of the same signals as theyarrive at the receiving station.

Figure '3 illustrates the received, current curve when interpolated inaccordance with my invention.

F igurc 4 is a diagrammatic view of the circuit and apparatus in oneembodiment of myv invention.

Figure 5 shows a modification of the arrangement disclosed in Fig. 4.

Figure 6 is a modification of Fig. 4 show"- ing the condenserinterpolating method at a terminal printing station. a .1

Figure 7 is a modification of circuits and apparatus of the condenserinterpolating method employing a three position relay interposed betweenthe amplifier and the re peating relay at the receiver station.-

Figure 8 is a diagram of the circuits. and

apparatus of a modified form of the condenser interpolatingcircuitemploying tuning forks at the receiving station. 7

In Fig. 4, a cable 1 extending from a remote station (not shown) tostation A is connected in series with the input of amplifier 2comprising any well known type of distortion correcting network andcurrent amplifier, the opposite terminalof the amplifier 2, beinggrounded at a sea earth 3. The output of the amplifier 2 is connected toa line winding 4; of; relay 5 which comprises in addition to this mainorline winding. a. re-

versing winding 6. One terminal of the re- 'versing winding 6 isconnected-to the arma ture 7whieh is operatedto either of its contactsconnected to opposite terminals of abattery under 'joint control of thewindings 4 and 6 in amann'er to be described in more detail hereinafter.The other terminal, of winding 6 is connected to one side of condenser8. Winding 6 and. condenser 8 are shuntedby a resistance 9 whichprovides a I discharge path for the condenser 8-a s will,be described indetail hereinafter. Connected to the common terminal of the condenser 8and resistance 9 is the continuous relation is such that the brush 14.will move 11 of the rotating receiver distributor 12. The receiverdistributor 12, which in ractice is circular in form, is here shown at,for pui'pose of illustration and comprises in addition to the solid.ring 11, a segmented ring 13 and a brush 14 bridging the segments of thering 13 and the solid ring 11.

The dimensionsof the segments and speed -of the brush rotation is sochosen'thatthe brush 14 will wipe over two segments durmg a singleimpulse period and the phase into engagement with a dead segment markedD during the first half of the impulse and will pass over the succeedinglive segment L during the last half of the signal period as clearlyindicated by a comparison with Figures 1-3 in which time is measuredalong the horizontal as in Fig. 4. By dropping vertical lines betweenasignal interval on Figs- 1-3, it: will be noted that they included a Dsegment and an L segment on ring 13-. No driving motor or synchronizingand phase correcting mechanism is shownas any well known apparatus maybe employed.

As shown, the alternate segments L, of the segmented ring 13 aremultipled to each other and connected to the winding 15 of the storingrelay, the other terminal of which is connected to-the mid-pointaof thebattery. The armature 16 of the storing relay is connected to thereceiving magnets of a printer through additional rings of thedistributor, (not shown) or it may be connected to a cable for repeatingthe impulses to a remote station. 1 e I The operation of the arrangementshoivn in Fig. 4 will be described in connection with the Figs. 1 to 3,which illustrate the wave shape of the transmitted and received signals.It will be understood that the brush 14 is driven by a synchronous motor(not shown) in synchronism with the transmission of the code signals.For the purpose of describing the operation of my invention, it will beassumed that a code combination of impulses as indicated between M and NFig. 1, comprising a spacing-marking-spacing-marking marking combinationof impulses is impressed on the cable 1 at the transmitting station.The'shape of the wave received at station A will take aform'approximating that shown in Fig. 2. It will be noted that theimpulse preceding the first code impulse is a spacing signal. Thisreceived impulse is so attenuated that it has no effect on the linewinding 4. Inasmuch however as the first code impulse which follows isof the same polarity, the amplitude of the current flow which graduallyincreases as the length of time during which the impulse islll'lplthsttl on the line becomes longer. will become commensurable asshown at b, Fig. That is, sufficient energy is developed by this time toproduce a spacing signal during the second impulse of the same polarityor in this case the first impulse of the code under consideration. Thesecond, third, and fourth signal impulses, however, are high frequencyunit length impulses and are therefore on the line an insuflicientlength of time to reach any measurable amplitude. Accordingly theyproduce no effect as indicated at c, d and c, Fig. 2. The fifth signalimpulse, however, being the second of a prolonged marking signal, willhave accumulated suflicient energy to produce an effect on the receivingcoil as shown at f in Fig. 2.

It is evident from an inspection of Fig. 2, that some means arenecessary for interpolating the high frequency signals which produce 'noeffect on the receiver as indicated at 0, a3 and e, Fig. 2, if thereceiver is arrives when bru'sh 14 is on the first segment D, ustunderneath the left half of impulse b, has a wave shape as. indicated'at Fig. 2 and flows over the cable 1 through the amplifier 2 to a seaearth return circuit at 3. As a result current of sufficient amplitudeflows in the-output circuit of the amplifier and through the coil 4 tooperate the armature 7' to its spacing or left hand contact. A circuitis completed from the positive side of battery, to the left hand contactand armature 7, parallel paths through resistance 9 and winding 6 of therelay 5, the condenser 8, to solid ring 11, brush '14 and second segmentL of ring 13 which is underneath the right half portion of the impulseI), over which it is assumed the brush is at that time moving. Thiscircuit is completed through the winding 15 of the storing relay to themid-point of the same battery. The current flowing over this circuitpasses through the winding 6 in a direction to aid the current flowthrough winding 4. described above and accordingly maintains thearmature 7 in engagement with its left, hand contact.

An important distinction over the prior art will be observed from thedescription thus far given. Whereas in the Clokey arrangement, the linecurrent, in order to prevent the armature from moving to its alternatecontact, must he of suiticientjamplitude to overcome the local currents,in the present case, the brush 14 is on a dead segment D during theintervalat the beginning of' ginal character is thu" very much reducedover the arrangement proposed by Clokey. As a result of the irirrentflow through winding 15, armature 1"} moves into engagement with itsleft hand contact to connect the positive side of battery to a localprinter (not shown) or to another cable section.

When now the brush 14 moves into engagement with the second dead segmentD, on the ring 13, the local circuit for winding 6 is opened. At thistime the current of substantially zero amplitude arrives over the cableas indicated at 0 and there is therefore no current flowing throughwinding 4. The

.condenser 8 which had beencharged, as described above. now dischargesitself through the winding 6 and resistance 9 in the opposite directionfrom that traced above. As a result of this current flow in the oppositedirection, the armature 7 is moved into engagement with its right handcontact.

This operation, it will be noted, takes place duringthe first half ofthe second signaling. period c. When the brush 14 moves into engagementwith the fourth segment L, a

cuit is completed from the negative side of battery, through armature 7and over the circuit including windings 6: and 15. This current flow isin the opposite direction from that produced by the positive side ofbattery but in the same direction as the first discharge from condenser8 and hence maintains the armature 7 in engagement with its left handcontact. I The current flow now to the winding 15 will swing thearmature '16 into engagement with its righthand-contact and will repeata marking impulse.

As the brush 14 moves into engagement with the third dead segment I),the charged condenser 8 again discharges, causing a flow of current inthe opposite direction from that described just above but in the samedirection as the original flow of current pro duced from the positiveside of battery and the armature 7.is accordingly thrown into engagementwith its left hand contact, as in the first instance. Upon engagement ofthe 6th or live segment L, by the brush 14, a current flows through thewinding 6 over a circuit as originally traced, as a result of which thearmature 7 is maintained in engagement with its contact and the armature16 is moved 1 into engagement with its left hand. contact. As the brush14 moves into engagement with its 7th and 8th segments the sameoperations .as' described in connection with the 3rd and 4th segmentsoccur.

Vhen, however, the brush 14,mo ves into engagement with its 9th segmentD, a change in operation from thatalready shown occurs. In Fig.1 it willbe noted that impulse f is the second of two succeeding impulses of thesame polarity. The current amplitude therefore increases sufficientlyduring this impulse interval as indicated in Fig. 2 at f gages the 9thsegment D, a discharge occurs from the condenser 8 through the coil 6which is in a direction to move armature 7 to its opposite position fromright to left. The

current flow through windingA is, however,

of sufficient amplitude now to prevent this movement of armature 7 whichis therefore mamtamed in engagement with its rlght hand contact insteadof being moved to its left hand contact as would normally have occurred.had there been no current flow through the winding 4. When now thedistributor brush 14 moves into engagement with its 10th segment, thecurrent flow through the storing relay 15 is from the negative side ofbattery at armature 7, and accordirigly the armature 16 is maintained inengagement with its right hand contact. At

"this time also it will be noted that the current flow through thecoil 6is in a direction to aid the coil 4.

\ It will be. clear from the above description, that the receivedsignals are inte1 polated in such a manner as to operate the receivingapparatus with signahngwaves of the same wave shape as those transmittedfrom the transmitting station. The operations are performed by asimplified mechanism in which a single distributor ring functions incooperation with a condenser, which is arranged to charge and dischargealternately, producing as is well known, momentary surges. Accordingly,the line relay 4 is not opposed by a continuous current flow in thereversing coil but rather by a single instantaneous current flow andduring part of the impulse interval is aided by current in the reversingcoil. As will be noted from acomparison with the patent referred toabove, the interpolating operations are here performed by a singlecondenser which had previously required an additional set of distributorrings and extra reversing coils in which the opposing winding flow iscontinuous. It will further be noted that the relay 15 is operatedduring the second half of the impulse interval when the line winding isbeing aided ,by winding 6. Furthermore during the first portion of theimpulse interval, the reversing relay functions independentlyof thedistributor although in synchronism with the signals.

- As shown in Fig. 4, the condenser is consegment L of the segmentedring 25, a circult is completed from battery through armature 26, ring27 and the storing relay 28 for operating the armature 29 connected to arinter or repeating circuit (not shown). %urrent also flows at this timethrough the inductance 21 which shunts the coil 22. When the brush 24moves into engagement with a dead segment D the charge in inductance 21discharges through the reversing coil 22 in the opposite direction fromthat of the original flow of current for operating the armature 26 toits opposite contact.

The main line winding 31 is connected to the output circuit 32 of theamplifier 33, the input circuit of which is connected to the cable 34and sea earth 35. The operation in this figure is otherwise similar tothat described in connection with Fig. 4.

It will be noted in connection with the operation described in Figs. 4and 5, that the line relay is operated in accordance with both positiveand negative impulses to operate a two position storing relay, such asrelay.15. In operating a printing telegraph apparatus, however, it ismore usual to employ magnets which will respond to marking impulses andfail to respond tospacing impulses or vice versa. In such cases it isnecessaryto arrange the circuits so that no current flows during thespacing impulse interval and accordingly no charge will collect on thecondenser 8 for reversing its armature in the manner described above. Inorder to overcome this difiiculty an arrangement such as disclosed inFig. 6 may be employed.

In this case, the cable 35 extending from the remote station isconnected to the input side of the amplifier 36, the opposite terminalof which is connected to the sea earth 37. The output circuit ofamplifier 36 is again connected as described in the first modificationsabove to the line winding 38 of the relay 39. In addition to the linewinding, the relay 39 comprises a reversing winding 41, one terminal ofwhich is connected to a condenser 42. The winding 41 and condenser 42are shunted by a resistance 43 which at the terminal connected to thecondenser 42 is connected to the mid-point of a battery. The oppositeterminal of winding 50, driven by a motor in synchronism with thereceived impulses as described above. The solid ring 48 is connected tothe armature 51 of the vibrating relay 39. The segments of ring 49 areconnected to the receiving magnets 52 of the printers.

'peatmg described above and brush 50 moves into engagement with an evennumbered segment, a circuit is completed from the battery througharmature 51, ring 48, brush 50, segmented ring 46, through the leakrecord instrument 44, winding 41, condenser 42 and to the mid-terminalor split of the battery. The condenser 42 is charged and will laterdischarge through the coil 41 and resistance 43 when the brush 50 is ona dead or odd numbered segment. A circuit is also completed from thebattery over the armature 51 and through a magnet coil 52 to battery.

If the brush 50 is on any segment of the first channel including thefirst five printer magnets 52, no circuit will be completed whilearmature '51 is in engagement with the-positive side ofbattery. When,however, the armature 51 moves into engagement with its right handcontact, thecondenser 42 will still be charged in the opposite directionbut the In the apparatus disclosed in Figs. 4, 5 and 6, a twopositionrecelving relay is shown. In some systems it is desirable to employ athree positioned relay interposed between the amplifier and therepeating or printing relay. This is accomplished in the mannerillustrated in Fig. 7.

Relay '55, instead of being connected directly to the amplifier, as inthe above described figures, is connected to the armature 56 of thethree positioned relay 57. As shown, the armature 56 is normallymaintained by springs-58 and 59 in a mid-position between its contacts.These contacts are connected to the opposite terminals of bat.- tery 61.The winding. 62 of the three position relay is connected to the outputof the amplifier 63, the input of which is connected to the cable 64extending from a remote station and to ground at 65.

The armature 56 is connected to one terminal of the winding 66, theother terminal of which is connected to the midpoint of the battery 61.Line winding 66 and the reversing winding 67 comprise thev repeatingrelay 55 which is similar in structure to the rerelay employed describedmodifications.

Upon receipt of a signal of sufficient ampli- As the armature 51 ismoved intoengageexplained above occurs when two or more ment with one ofits contacts in the manner successive impulses of the same polarity arein the above transmitted over the cable 64, the armature 56,is movedinto engagement with one of its contacts to cause a corresponding fiowof current through winding 66 of the line relay 55. Line winding 66 ofrelay 55, in conjunctionwith the winding 67, condenser 69 and theshunting resistance 71, controls the vibrating operations of thearmature 72 which, through the solid ring 73 and segmented ring 7 4operates the storing relay 75, for either repeating the receivedimpulses or operating a printer (not shown). The opera- A tion of thisarrangement is similar to that of the previous modifications and neednot therefore be described in detail. During the interval of highfrequency signaling, i. e., of alternate marking and spacing impulses,each of a single impulse length, there is substantially no currentflowing in coil 62 as ex plained above. When, however, a succession ofimpulses of the same polarity flows through coil 62, current ofsufiicient amplitude is built up-to operate armature 56 into engagementwith one of'i'ts-contacts, thereby closing a circuit for winding 66. Atthis instant, the brush 68 is movingover an odd numbered or dead segmentand condenser 69 will be discharging a current through winding 67,tending to throw armature 72 to its opposite contact. The current in 66tends, however, to hold armature 72 in engagement with the same contactand is of sutficient amplitude to overcome the effect of the dischargecurrent through 67. Armature 72 accordingly remains on the same contactand maintains the current through storing relay 7 5 in the samedirection, when the brush 68 moves on to the succeeding even numberedsegment. 'At the same time the current through winding 67 is such as tomaintain armature 72 in the same position and condenser 69 is againcharged in such manner that upon discharge, it will energize coil 67 forthrowing armature 72 to its opposite contact.

It will be recalled that the present invention is directed to replacingthe distributors and extra auxiliar vibrating relays and vibrating ringsan brushes in the method proposed by Clokey, by impedances which are soarranged as to perform substantially the same function.

In Fig. 8 I disclose a further modification of my invention in which thedistributor and its accompanying problem ofsynchronization is entlrelyeliminated. In this figure, the input of amplifier 81 is connected atone terminal to the-cable 82 extending from a remote station to thelocal station, and the other terminal is connected to the earth at 83.The output of the amplifier is connected to the line coil 84 and drivingrelay winding 85 in series. As in the previous cases, the linerelaycomprises in addition to the 'line coil 84, a reversing coil 86connected in series with' a condenser 87,

the relay 86 and condenser 87 being shunted.

by a resistance 88. One terminal of this network is connected to thearmature 89 of the reversing relay 86 and the other termigraph systems,comprising tines 93 and 94 properly supported on a base and providedwith weights or other means for adjusting the frequency at which thesetines vibrate. drivin magnet 95 is connected to one contact of thearmature 96 of the driving relay 85. The other terminal is connectedthrough a resistance 97 to the positive side of the battery. A condenser98 is connected engages its left hand contact as will be describedhereinafter.

The fork 93 is connected to the winding of the storing relay 99,. theopposite termito armature96 andshunts resistance 97 I over which itdischarges when armature 96 nal of which is connected to the mid-pointof battery. The armature of storing relay 99 operates between itscontacts to complete a circuit for a printer magnet or-for repeatingover a cable in a manner well understood.

. The operation of the a paratus described in Fig. 8 is as follows hetuning fork 92 is first adjusted to vibrate at a frequency equal to therate at which signals are being received, so that the fork 93 forexample, will oscillate from one contact to its alternate contact duringan impulse interval,

the latter half of a signaling period and the current flows from thepositive side of battery through the armature89, parallel paths throughresistance 88 and the winding 86 condenser 87, to contact 91, fork title93 and the winding of relay 99 to the mid-point of the battery. Therelay 99 is energized to operate its armature 100 in engagement with itsleft hand contact for completing a circuit from the positive side ofbattery to either a repeating cable or receiving printer magnet as thecase may be. The current flowing through the winding 86 issuc'h as tomaintain the armature .89 in engagement with its left hand contact. Asthe tuning fork now moves into engagement with the opposite contact atthe beginning of the succeeding impulse period, the condenser 87, whichwascharged by the current flow described above, now discharges andcausesa current to flow through the winding 86 in} ing the fourth and fifthimpulses. The fork magnet 95 of the tuning again engages its left handcontact during the second half of the second impulse period, an impulsefrom the negative side of batter \is sent through the windings 86 androm that originally described and moves armature 100 into engagementwith its right hand contact. The current flow in this case is in such adirection through. the winding 86 as to maintain the armature 89inengagement with its right hand contact. The above described cycle ofoperations will then be repeated.

When, however, a current of the same polarity continues for twosignaling periods, the current flow throughthe coil 84 is in theopposite direction and of sufficient amplitude to overcome the currentflow through the winding 86 and, as a result, the armature 89 is heldagainst whichever contact'it happens at that time to engage. The storingrelay 99 is thus operated by two successive impulses of the samepolarity, as the tuning forkmakes two complete cycles. Thus for example,if the fourth and fifth impulses are of the same polarity as illustratedin Fig. '1, the armature 89 remains in engagement with its right handcontact durtine 93' engages its contact 91 and completes a circuitthrough the condenser 87. The current flow through .the coil 84,however, is at this, time of sufficient amplitude to maintain thearmature in engagement with its right hand contact, and when 'thereafterthe tuning fork again engages its contact 91, 'a circuit from thenegative side of battery is a second time completed for the. storingrelay 99.

At this time the current flow through the relay will also be suflicientto move the armature 96 into engagement with its right hand contact anda circuit is completed from the.positive battery through the condenser98, armature 96 and through the driving fork to negative battery. Itwill be noted that the current flows through relay 85 at the beginningof the impulsing eriod when the fork tine 93 should normal y be inengagement with its right hand contact 91'. The energization of relay 95at this time will therefore pull the forks inwardly in the event thatthey are out of synchronism with the signals. In this mannersynchronization of the tuning fork occurs atperiodic-intervals undercontrol of the signalingimpulses themselves to pull the fork intosynchronism in case it is out of synchronism to any extent at thatinstant.

.lil' will be clear that by the use' of tuning .fork, synchronism ismuch morereadily obtained than with distributors. The mechanism employedis notonly' simpler but more he current flows throufgh the winding 99 inthe opposite direction rugged, more easily adjusted and generallybettcradapted for the purpose in hand. Although I' have disclosed myinvent on in connection with a specific form or application'thereof, itwill be clear, that there are many other forms in Which'the inventionmay be practiced and I do not intend tolimit myself by this specificarrangement except insofar as set forth in the appended claims.

I claim:

l. .Incombination, a receiving relay comprising a line winding and areversing winding, a distributor connected to said reversing winding, acircuit independent of the dis tributor for energi' zing said reversingwinding during the first half of each signal interval-and meansincluding said distributor for completing an energizing circuit for saidreversing winding during the remaining period of each signal interval.

-2.' -In combination, a receiving relay comprising a line Winding and areversing Winding, a condenser connected in series wit-h saidreversingwindi'ng, a distributor, means including said distributor forcompleting a circu t for said reversing coil and said condenser. and.circuit means independent of said distributor for energizing saidreversing coil during the remaining portion of the signal interval.

3. In a telegraph system over which the received signals areconsiderably attenuated, and in which the receiving apparatus includes arelay having an armature, the method of operating the receiver withrespect to the signals which comprises vibrating the armature insynchronism with the signals,- mainta ning the relay armatureopen-circuited during the first half of a sig nal interval and in aclosed circuitduring the second half of the signal interval.

, 4. In a telegraph system over which the transmitted signals areconsiderably attenuated, and in which the receiving ap aratus includes arelay having an armature, the method of operating the receiver whichcomprises operating the relay in accordance with the received signals,maintaining the relay armature open-circuited during the first portionof a signal interval and ina closed circuit during the remaining portionof the sigwinding to maintain the armature in 1 w ichever poslti'on 1thas assumed during,

the remaining portion ofthe signal interval.

6. The method of o crating a relay a1 rangement of the Go stad typeincluding a local winding and its armature, which comrises producingcurrents in'the local winding tending to reverse the armature positionduring the first portion of a signal interval and thereafter invariablyproducing currents to maintain the armature in whichever position it hasassumed during the remaining portion of the signal interval.

7. The method of operating a relay of the Gulstad type provided with aline winding, a local winding and an armature, which comprises sendingamomentary current flow through the local winding tending to reversening of each signal interval, successively alternating in direction witheach signal interval, and tending to throw the armature to its oppositeposition, producing a current flow in the line winding in the event of asuccession of impulses of the same polarity v of suflicient amplitude toprevent the armature from moving to its alternate position at thebeginning of the impulse interval and thereafter durin the remainder-ofthe signal interval pro ucing a. current flow in the reversing windin inthe opposite direction to that produce during the beginning of thesignal interval for maintaining the armature in its position.

9. In combination a telegraph cable, a line coil connected to saidcable, a condenser and a reversing coil, said reversing coil beingconnected in series with said-condenser and its armature, a relay, meansincluding circuit connections for maintaining said reversing coilcircuit open during the beginning of a signal interval, said means beingarranged to connect said reversing coil to said relay during theremaining portion of said signal interval.

10. In comb nation a cable, a relay comprising a line coil connected tosaid cable, a reversing coil and the armature; a distributor comprisingsegmented rings connected in series w'th said reversing c011 and a relayconnected to the segments of said segmented ring.

- ing coil, adistributor connected to said 0011'- denser and meansincluding said distributor for charging the condenser and a circuit fordischargin said condenser through said reversing coi 12. In combinationa receiving relay comprising a line coil and a reversing coil, acondenser connected in series with said reversing coil, a resistanceconnected inshuntto said reversing coil and said condenser, meansincluding a distributor for charging said condenser, said distributorbeing arranged to suecessively permit said condenser to charge throughsaid reversing coil and to discharge through said resistance.

13. In combination, a receiving relay comprising a. line coil and areversing coil, a condenser connected in series with saidreversing coil,a resistance connected across said condenser and reversing coil, abattery, means including said distributor for connecting saidcondenserand reversing coil to said battery,

said distributor being arranged to periodically disconnect said batteryfrom said condenser, whereby said condenser discharges through saidreversing coil and said re-v sistance.

14. In combination, a receiving relay comprising a line coil and areversing coil, a condenser connected in series with said reversingcoil, a resistance connected across said condenser and said reversingcoil, 8. battery, means including said distributor for connecting saidcondenser and reversingcoil to said battery, 'said distributor beingarranged to periodically disconnect said battery from said condenser,whereby said condenserv discharges through said reversing coil and saidresistance, and a second relay connected to said condenser through saiddistributor an interval after the beginning of the impulse interval.

15. In'combination a receiving relay comprising a line winding, areversing winding and armature, a condenser and resistance connected inseries with'said reversing winding, a distributor comprising a first anda second segmented ring, a plurality of magnets connected to said secondsegmented ring, said ,first segmented ring being arranged tosuccessively connect said receiving relay to its own armature and saidsecond segmented ring being arranged to connect said magnetsto saidarmature.

1 16. In a telegraph receiver comprising a distributor provided with asegmented ring having alternating live segments and open or deadsegments, and abrush wiping thereover, the method of operating thedistributor with respect to the signaling impulses, which comprisesrotatin the brush over an open circuited segment uring the beginning ofan impulse intervaland over a live segment during the remaining portionofthe signal in- .17. In a telegraph receiver, a segmented. ringdistributor, a'brush moving over said distributor, alternate segments ofthe. distributor ring bein multiplied, a relay connected to saidmuftiplied segments, and the remaining segments of said distributorbeing open-circuited the method of operating the dlstributor withrespect to the signaling 5 impulses which comprises moving the brushover one of the open circuited segments during the beginning of a si a1interval and over a multiplied segment uring the remaim in portion ofthe signal interval.

n testimony whereof I aflix m signature.

' MARION H. WOO WARD.

